Ageing effect on electrical properties of the oxyapatite/Nd2NiO4 interface

In the present work, the influence of the ageing process on the electrical properties of the oxyapatite La10Si5.5Al0.5O26.75/ Nd2NiO4 interface is studied. Samples were submitted to a thermal treatment at 1200°C in air for different periods. X-ray diffraction and electron microscopy micrographs show a significant morphological change occurring in both electrolyte and cathode components after 309h. An important degradation of electrical properties versus time was observed. Conductivity results show an increase of the activation energy and a decrease of the pre-exponential factor for the bulk and the grain boundary of the La10Si5.5Al0.5O26.75 electrolyte. Diffusion processes operating during the heat treatments might be involved to explain this behavior. Furthermore, an increase of the electrode resistance by a factor of 5 is observed. Finally, it is worth mentioning that no degradation of this interface was revealed after several periods of heat treatment at 1000°C in air.